Micromechanical sensors are hermetically closed, as a rule, by a wafer bonding process, in order to protect the sensors from environmental influences (such as dust, moisture, gas etc.) and to enclose certain gases or a vacuum. In this instance, various wafer bonding methods have become established, such as eutectic bonding, glass frit bonding, and thermocompression bonding.
In eutectic bonding, a possible material combination is aluminum and germanium, which are typically respectively deposited on a sensor wafer and cap wafer.
In comparison to glass frit bonding, the space requirement in eutectic bonding for a hermetic and mechanically firm connection is clearly lower, based on the overall lower material quantity of the “joining material.” However, upon melting, the eutectic material becomes liquid, and therefore requires lateral distances from active and movable structures, so that, in this way, disadvantageously, a relatively large space has to be kept in reserve.
German Document DE 10 2011 077 933 A1 describes a method for bonding two substrates, particularly in the production of eutectically bonded semiconductor components having microelectromechanical patternings.